Page 176 - Start Up Mathematics_5

Finding Area by Formula length (l)
S R
Area of a rectangle

Length of rectangle PQRS (l) = 8 units breadth (b) breadth (b)

Breadth of rectangle PQRS (b) = 5 units
P Q
Area of rectangle PQRS = l × b = (8 × 5) square units length (l)

= 40 square units

Area of a rectangle = Length × Breadth = l × b
Area
Length of a rectangle =
Breadth
Area
Breadth of a rectangle =
Length

Example 10: Find the area of a rectangle whose length is 11 cm and breadth is 7 cm.

Solution: Length (l) = 11 cm, Breadth (b) = 7 cm

Area of a rectangle = l × b = 11 cm × 7 cm = 77 cm 2
2
Example 11: The area of a rectangle is 36 cm . If its length is 9 cm, find its breadth.
Solution: Area = 36 cm Length = 9 cm
2
Area 36 cm 2
Breadth = = = 4 cm
Length 9 cm
So, the breadth of the rectangle is 4 cm.

2
Example 12: The area of a rectangular garden is 220 m . If its breadth is 10 m, find its
length.

Solution: Area of the garden = 220 m 2
Breadth of the garden = 10 m
Area 220 m 2
Length of the garden = = = 22 m
Breadth 10 m
So, the length of the rectangular garden is 22 m.

Area of a square side
D E
Side DE = 4 units Side EF = 4 units
Area of square DEFG = (4 × 4) square units = Side × Side side

Area of a square = Side × Side G F

Example 13: Find the area of a square whose side measures 7 cm.
Solution: Side of the square = 7 cm

Area of the square = Side × Side = 7 cm × 7 cm = 49 cm 2

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